1. Field of the Invention
The present invention relates to power control systems and, more particularly, but not by way of limitation to an electronic power control system for motors such as compressor motors, pump motors, fan motors and the like.
2. Description of the Related Art
A typical power control system is mechanical and includes a sensor and a relay responsive to the sensor for delivering power to a motor. Sensors commonly employed in power control systems include ice bank sensors, liquid level sensors, pressure sensors, temperature sensors, and the like. Upon the detection of a first predetermined condition, such as a low liquid level or a certain temperature, the sensor outputs a signal that actuates the relay, thereby mechanically closing the contacts of the relay to connect the motor to a power source. The relay remains actuated and the motor continues to run until the sensor detects a second predetermined condition, such as a full liquid level or desired temperature. When the sensor detects the second predetermined condition, it ceases outputting its signal, resulting in the contacts of the relay opening to remove power from the motor.
Although the above mechanical power control system operates adequately, it suffers a significant disadvantage in that its relay is subject to malfunction. The relay typically malfunctions due to the fusing of its contacts, which means the motor receives power regardless of the signal output by the sensing device. As a result, the motor runs continuously, which burns out the motor and possibly damages the entire system. Furthermore, a system malfunction producing an accident may occur. Consequently, a mechanical power control system is unreliable and often results in a situation where all or part of an entire system must be unnecessarily replaced.
Accordingly, an electrical power control system that eliminates the unreliability associated with relays will significantly improve over current mechanical power control systems.